In some applications, signals are processed digitally, converted to analog signals, and then mixed with a local oscillator signal to obtain a signal with a desired frequency. Wireless transmitters are an example of such an application, as signals are processed digitally at a so-called baseband frequency, converted to an analog signal via a digital to analog converter (DAC), and mixed with a radio frequency (RF) signal to obtain a radio frequency transmit signal, which is then passed through a power amplifier and transmitted via an antenna.
Previous transmitter architectures have been built as current steering DACs, wherein a controller changes control signals that are provided to gates of transistors in a cell array of the DAC, to thereby control the corresponding output current from the DAC. Unfortunately, these previous architectures suffer from shortcomings in that they exhibit non-linearities and low-efficiency, because the current sources waste a significant amount of power. As will be appreciated in more detail herein, the present application provides DACs that use capacitive cells, rather than current steering cells, to realize a more efficient solution.